Silt dredging method

ABSTRACT

A method involving two aspects. One comprises dragging a suitable scraper from a position remote from the shore of a body of water toward it and lifting the scraper, i.e., not dumping it, at the place the silt is to be deposited above its load of silt. The second aspect, which can be used alone or preceding the first comprises dragging the scraper along the bottom of the body of water only in the area to be deepened to loosen and agitate the silt to put it in suspension so that normal currents in the body of water carry it towards the shore. Thereafter, if desired, and with relatively short path of travel, a scraper can pull redeposited silt near the shore onto it.

United States Patent 1 91 Loy [54] SILT DREDGING METHOD [76] Inventor:Henry Albert Loy, 87 North 1 1th W.,

Provo, Utah 84601 [22] Filed: Mar. 24, 1972 [21] Appl. No.: 237,757

Related [1.8. Application Data [62] Division of Ser. No. 54,910, July13, 1970, Pat. No.

11/1957 Schofield 172/265 5/1918 Pratt ..172/26.5

. Primary ExaminerRobert E. Pulfrey Assistant Examiner-Clifford D.Crowder Attorney-George H. Mortimer [57] ABSTRACT A method involving twoaspects. One comprises dragging asuitable scraper from a position remotefrom the shore of a body of water toward it and lifting the scraper,i.e., not dumping it, at the place the silt is to be deposited above itsload of silt. The second aspect, which can be used alone or precedingthe first comprises dragging the scraper along the bottom of the body ofwater only in the area to be deepened to loosen and agitate the silt toput it in suspension so that normal currents in the body of water carryit towards the shore. Thereafter, if desired,,and with relatively shortpath of travel, a scraper can pull redeposited silt near the shore ontoit.

4 Claims, 6 Drawing Figures 3,679,004, granted July 25,

1 SILT DREDGING METHOD REFERENCE TO EARLIER FILED APPLICATION Thisapplication is a division of my prior application Ser. No. 54,910 filedJuly 13, 1970 entitled SILT DREDGING APPARATUS, now US. Pat. No. 1972,for DRAG SCRAPER FOR DREDGING SILT.

BACKGROUND OF THE INVENTION Lakes are fed by rivers and streams carryingsilt in suspension that settles out in the relatively quiescentconditions prevailing there. This silt builds up on the bottom of thelake and, over a period of years, raises the level of the water,assuming approximately constant volume of water in the lake, and floodsland adjacent to the shore. A somewhat similar build up of silt takesplace in portions of the beds of the rivers flowing into and from thelake where the rate of flow of the water is slow compared to the ratewhere silt is picked up. The problem of silt build up in the beds oflakes and rivers has long been recognized and many devices and methodshave been proposed for dredging the beds of rivers and lakes. Many ofthese devices are complex pieces of equipment that are expensive tomanufacture and use.

SUMMARY OF THE INVENTION The present invention relates to a method ofdredging silt from lake and river bottoms, preferably using the novelapparatus disclosed herein which is claimed in my said priorapplication.

The apparatus preferably used in carrying out the method comprises asimple and relatively inexpensive scraper and catamaran for moving thescraper to a position remote from the shore so that it can be pulled into the shore to deposit the load of silt by merely lifting the scraperabove the load. The scraper can also be used to agitate deposited silt aconsiderable distance from shore to resuspend it in the water that hascurrents normally moving shoreward where the silt will settle again andcan be removed to the shore by rela tively short travel of the scraper.V

FIG. 1 is an isometric view of the scraper from above the right rearcorner; I

FIG. 2 is a side view of the right side of the scraper;

FIG. 3 is an isometric view of the interior of the scraper from belowlooking into it from the front;

FIG. 3a is a detailed view of a portion of the scraper of FIG. 3;

FIG. 4 is an isometric view of the catamaran with the scraper in raisedposition; and

FIG. 5 is an isometric viewof a toothed blade that may be removablysecured to the scraper to loosen compacted silt.

DESCRIPTION OF THE INVENTION The method of the invention involves twoaspects which can be practiced independently but preferably are used incombination, one preceding the other, where a lake or large body ofwater is to be deepened aconsiderable distance from shore. One aspectcomprises bringing silt from the bed of a lake or river to the shore anddepositing it there, i.e., near or on the shore,

by use of a scraper, preferably the novel scraper described herein, andmeans to move it repeatedly toward and away from the shore andprogresively along it. A second aspect comprises dragging a scraper,again preferably the novel scraper described herein, along the bottom ofthe body of water only in the area to be deepened to loosen and agitatethe silt to put it into suspension in the water so that normal currentsin the body of water carry it from the area where agitation suspends ittoward the shore where it redeposits or settles out. Thereafter, ifdesired, and with a relatively short path of travel for the scrapertoward and away from the shore, the redeposited silt can be brought tothe shore as described in the first aspect of the method of theinvention, thus using both aspects of the method in combination, i.e.,in sequence, for a single purpose.

The first aspect of the method of dredging silt from the bottom of abody of water, e.g., a lake or river, in accordance with the inventioncomprises placing a scraper, preferably the scraper of the invention asdescribed above, on the bottom of the body of water with the front endpointed in the direction of the shore. The distance of the scraper fromthe shore may be varied and depends on the circumstances and theequipment being worked with. For example, if one is dredging near toshore the scraper may be used with a crane that has vertical andhorizontal movement generating means. Then the scraper. is dragged alongthe bottom toward the shore by using the horizontal movement generatingmeans attached to the chain 40 or 48 as circumstances require. When thescraper is on the shore at the place where its load of silt is to bedeposited, the scraper is moved backward and/or upward away from itsload of silt without being turned over, e.g., the vertical movementgenerating means may lift the scraper to deposit through the open bottomthereof the load of silt it has brought up with it from the bed of thebody of water as it was dragged along it. If one is dredging from aconsiderable distance from the shore, the catamaran 5 is used to takethe scraper to the site to be dredged, the winch 66 is operated to lowerthe scraper to the bottom of the body of water, the catamaran is thenmoved, either by power supplied from an outboard motor secured to theframe 52 or by a power boat ahead of the catamaran which tows it towardthe shore and simultaneously pulls the scraper. When the catamaran isclose to the shore the winch is operated to lift it from its load ofsilt which can then be brought near to or onto the shore as describedabove.

Another way of operating the scraper 1 involves use of the catamaran 5anda winch or windlass (not shown) anchored on the shore. The catamarancarries the scraper to the place remote from shore that is to be dredgedwith the wire rope or chain of the .windlass on shore attached to thechain 40 or 48. The windlass 68 on the catamaran lowers the scraper tothe bottom of the body of water with the front end aimed at the shore.The windlass on shore then reels in the chain or rope pulling thescraper and catamaran to the shore. When the floats 50 reach the shorethe reel 68 plays out its rope to permit the scraper to be pulled up onthe shore The second aspect of the method is based on the discovery thatsilt at points distance from the shore of a lake can be moved largely bynatural currents in the water to the shore by agitating the silt in thearea to be deepened, e.g., a considerable distance away from the shore,to resuspend it in the water. The natural currents then move thesuspended silt toward the shore and redeposit it there where it can bepulled up on the shore in the manner described above. In using thescraper 1 for this purpose it is towed along the bottom of the lake inin the area that is to be deepened by a power boat connected to thechain 40 or 48. Even though the scraper fills up with silt, it still isable to loosen other silt and agitate it to suspend it in the water nearthe point of agitation. The normal currents of the lake that move towardthe shore bring the suspended silt to the shore where much of itredeposits near enough to be removed by crane operation of the scraperas described.

The preferred apparatus for dredging silt comprises a scraper l and acatamaran 5.

The scraper 1 comprises a top wall 10 of rectangular shape, preferablyapproximately square and while not restricted to any particular size andgauge a convenient and practical size is about 6 feet by 6 feet by :6inch thick. Secured to the top wall 10 are side walls 12 and a rear wall14. These walls may be integral with the top wall, i.e., part of thesame steel plate, or they may be separate pieces of steel plate ofsimilar gauge suitably welded together along their contacting edges. Theside walls may have any suitable width, e.g., about 24 to 26 inches, andthe same length as the top wall. The rear wall 14 may be narrower thanthe side walls, e.g., about 14 to 16 inches wide and the same length asthe width of the top wall. There is no front or bottom wall, thusleaving the front and bottom open, as may best be seen in FIG. 3.

Secured to the rear wall 14 is a scraper blade 16 that is slopeddownwardly and forwardly at any suitable angle, e.g., at an angle ofabout 36 to the top wall 10. It preferably has the same length as therear wall 14 so that it may be secured at its ends to the side walls 12as well as along its upper edge to the rear wall 14, e.g., by welding.The blade 16 may have any suitable width but it is preferred to make itwide enough to extend a short distance below the plane of the bottomedges of the side walls 12, as may be seen in FIGS. 2 and 3, and a widthof about 18 inches is satisfactory for this purpose. v

The front ends of the top and side walls are preferably reinforced byspaced flanges l8 and 20 made from similar steel plate which aresuitable secured, preferably by welding, to these walls along theircontacting areas.

Preferably the side walls 12 have secured thereto, e.g., by Weldingalong the contacting areas, an outwardly extending shoe 22 whichdesirably is about the same length and gauge as the side wall. The shoes22 should be secured to their respective side walls adjacent to butspaced from the bottom edges thereof, e.g., some or 6 inches from thebottom edges, and they may have any desired width that will serve toprevent the scraper from sinking too deeply into loose silt it is toremove by scraping along the bottom of a body of water. A width of about5 inches has been found to be suitable for the shoes of a scraper of thedimensions and weight described above. The front ends of the shoes 22are preferably secured to the flanges 18 and 20 which desirablyterminate at the shoes at their lower ends as seen in FIGS. 1, 2 and 3.The lower front comer of each side wall is preferably cut off at anangle below the shoe 22 to form a sloping front end 24. The lower rearcomer of each side wall is also preferably cut off to form a slopingrear end 26 to which the ends of the scraper blade 16 may be secured,e.g., by welding.

As the scraper is dragged forwardly along the bottom of the body ofwater being dredged it is desirable to provide water escape openings orholes to facilitate filling the body of the scraper full of silt. Suchopenings may be provided in the rearward part of the scraper, e.g., inthe top wall as shown at 28 and in the upper part of the rear wall 14 asshown at 30, i.e., adjacent to the juncture of the top and rear walls.

Means are provided for pulling the scraper in a forward directionincluding U-shaped hooks 32, 34, 36 and 38 inserted into holes drilledin the flange 1 8 with their ends welded to flange 20 as shown in FIGS.1, 2 and 3. A chain 40 of suitable length is provided which has its endssecured by hooks 32 and 38 to' opposite sides of the scraper adjacent tothe bottom ends of the flanges 18 and 20. These hooks are passed throughan end link in each end of the chain 40 before they are secured asdescribed to the flanges. The chain 40 then runs up the respectiveflange 18 to hooks 34 and 36 which secure it at these intermediatepoints to the upper end of the flanges, again by passing through a linkthat is large enough to receive the hook as well as the other two linkswhich aresecured to it. The bight or connecting part of the chain 40 islong enough to form a V on top of the scraper 1 when laid on it, as seenin FIG. 1, with the apex at about the center of the top wall 10.

At the rear end of each shoe 22 a U-shaped hook 42 (only one shown inthe drawing) is suitably secured, e.g., by welding, with the end link ofa chain 43 held within the bight of the hook which extends beyond theend of the shoe 22, as seen in FIG. 1. This chain is somewhat longerthan the distance between the hooks 42 and may serve a number offunctions including a drag to stir up silt to suspend it, a pull chainto draw the scraper backwards, a lift chain for the back end of thescraper, used either alone or together with the front chain 40 so as togive the scraper any desired angle of inclination relative to thehorizontal, and the like.

Near the center of the rear wall 14 and at its upper edge, a U-shapedhook 44 may be provided which is suitably secured with the bight thereofabove the surface of the top wall 10. To the top wall 10 approximatelymidway between the side walls and somewhat forward of the center ofgravity an eye plate 45 may be suitably secured, e.g., by welding. In apreferred embodiment having a top wall about 6 feet square, the eyeplate 45 may be centered some 28 inches from the back and 44 inches fromthe front which is still somewhat in front of the center of gravity sothat if the scraper is lifted by the eye plate the front end will besomewhat higher than the back end, as seen in FIG. 4. These means makeit possible to lift the scraper in a number of ways, e.g., by an upwardlifting force on 45 alone, or an upward lifting force on both 44 and 45,or an upward lifting force on chain 40, chain 43 or both 40 and 43. Hook44 may also serve to hold chain 43 up while the scraper is being moved,if this position is desired.

Additional means for moving the scraper forward with the pulling forceat the proper height for varying conditions of the deposit on the lakeor river bed includes a bar 46 having a hook 47 at each end and a chain48 connected at its ends to said hooks which may be removably connectedto selected links of chain 40 between the hooks 32 and 34 and 36 and 38respectively, as may be seen in FIGS. 3 and 3a.

Referring now to FIG. 4, the catamaran 5 comprises two floats 50 whichmay be elongated hollow cylinders with tapered ends made of any suitablematerial and of sufficient length and diameter that they displace avolume of water equivalent in weight to the weight of the scraper andcatamaran without sinking too deeply into the water. The floats 50 arespaced apart a distance larger than the width of the scraper by a frame52 which comprises side bars 54 running along the floats a distancegreater than the length of the scraper 1 to which they are secured byany suitable means, e.g., bands 55, and cross bars 56 at the front andrear ends of the side bars to which they are suitably secured, e.g., bywelding. Spacing bars 57 may also be provided between bands 55 to whichthey are secured at their ends. Between the ends of the side bars 54 areuprights 58, the lower ends of which may be secured, e.g., by welding,to the side bars. A top bar 60 is suitably secured to the upper ends ofthe upright bars 58. Braces 62 are secured to the uprights 58 and theside bars 54 to hold the uprights and side bars in approximately rightangular relation to the uprights 58. A winch 66 is mounted on the topbar 60 which comprises a rotatable reel 68 mounted near the center ofthe top bar and a drive means 70 for the reel which may be of anysuitable kind, e.g., an electric motor, a crank or the like. A wire rope72 or the like has one end wound on the reel 68 and the other end may besecured to the scraper, e.g., to eye plate 45.

When the scraper I is lifted solely by the eye plate 45, and the plateis located somewhat forward of the center of gravity as described above,the scraper tilts to somewhat of an angle as seen in FIG. 4. If it isdesired to give the scraper a horizontal position when it is lifted, alifting force can be applied also to hook 44, either by a separate wirerope and reel or by suitably connecting a single lifting rope to bothpositions, as those skilled in this art will readily understand.Similarly a lifting force may be applied to the centers of chains 40 and43, if desired.

In some lake and river beds the deposits of silt become compacted sothat a plain scraper blade such as 16 does not readily loosen and scoopit up when the scraper is pulled forwardly. In such cases it ispreferred to secure to the lower edge thereof a toothed blade such asshown 11 FIG. 5 which comprises a steel bar 80, e.g., 5 inchesX6feethaving a plurality of teeth 82 welded therto which may be made ofsuitable steel, e.g., A X 2 X 15 inches, preferably with a sharpenedfront edge 84. The toothed blade may be secured to the lower edge of thescraperblade 16 in any suitable manner, e.g., by a plurality of boltspassing through openings 86 in the bar 80 and aligned openings in thescraper blade 16.

Although the method of the invention has been described and exemplifiedin connection with certain specific and preferred apparatus,modifications and variations can be made as those skilled in the artwill appreciate without departing from the principles of the inventionset forth hereinabove.

Having thus described and exemplified the invention, what is claimed is:

l. A method of dredging silt comprising dragging a scraper having top,side and rear walls and an open front and bottom with a forwardly anddownwardly sloping scraper blade at the rear along the bottom of a bodyof water from a position remote from a shore to ward it, supporting asubstantial part of the weight of the scraper on the surface of the siltoutside the side walls and a substantial distance above the lower edgesthereof during said dragging to control the depth of penetration of thescraper into the silt,.and moving the scraper from its load of siltwithout being turned over at the place the silt is to be deposited.

2. The method as set forth in claim 1 in which the scraper is movedrepeatedly toward and away from the shore and progressively along it.

3. The method of deepening a lake or like body of water in which normalcurrents are toward the shore comprising agitating the silt at thebottom in the area to be deepened to suspend it in the water so thatnormal currents therein carry it toward the shore and redeposit itnearer to the shore, and bringing the redeposited silt to the shore bydragging a scraper having top, side and rear walls and an open front andbottom with a forwardly and downwardly sloping scraper blade at the rearalong the bottom of said body of water where said silt has redepositedfrom a position remote from said shore toward it, supporting asubstantial part of the weight of the scraperon the surface of the siltoutside the side walls and a substantial distance above the lower edgesduring said dragging to control the depth of penetration of the scraperinto the silt, and moving said scraper from its load of siltat saidshore.

4. The method as set forth in claim 3 in which the scraper is movedrepeatedly toward and away from the shore and said slit is depositedthereon.

1. A method of dredging silt comprising dragging a scraper having top,side and rear walls and an open front and bottom with a forwardly anddownwardly sloping scraper blade at the rear along the bottom of a bodyof water from a position remote from a shore toward it, supporting asubstantial part of the weight of the scraper on the surface of the siltoutside the side walls and a substantial distance above the lower edgesthereof during said dragging to control the depth of penetration of thescraper into the silt, and moving the scraper from its load of siltwithout being turned over at the place the silt is to be deposited. 2.The method as set forth in claim 1 in which the scraper is movedrepeatedly toward and away from the shore and progressively along it. 3.The method of deepening a lake or like body of water in which normalcurrents are toward the shore comprising agitating the silt at thebottom in the area to be deepened to suspend it in the water so thatnormal currents therein carry it toward the shore and redeposit itnearer to the shore, and bringing the redeposited silt to the shore bydragging a scraper having top, side and rear walls and an open front andbottom with a forwardly and downwardly sloping scraper blade at the rearalong the bottom of said body of water where said silt has redepositedfrom a position remote from said shore toward it, supporting asubstantial part of the weight of the scraper on the surface of thE siltoutside the side walls and a substantial distance above the lower edgesduring said dragging to control the depth of penetration of the scraperinto the silt, and moving said scraper from its load of silt at saidshore.
 4. The method as set forth in claim 3 in which the scraper ismoved repeatedly toward and away from the shore and said slit isdeposited thereon.